A limitation of currently available hapten-based delivery platforms is the non-covalent linkage between hapten and the delivery vehicle. In applications for which a stable connection between delivery vehicle and payload is desired, non-covalent delivery vehicle-payload complexes may be unsuitable because non-covalently linked payloads may dissociate from the delivery vehicle.
This may pose a particular problem for toxic payloads that shall be targeted to e.g. tumors, and which cause adverse effects (i.e. non-specific toxicity) in case of premature liberation of the payload from the targeted delivery vehicle.
Different approaches are reported to address these drawbacks. However, none of these technologies provides for a robust and universal platform that enables delivery of toxic payloads, especially of toxic polypeptides, without off-target activity.
One approach is to fuse the payload to entities which stabilized the payload. Examples of such entities are human serum albumin or human immunoglobulin Fc-regions. This approach is applicable to many linear polypeptides that are composed of naturally occurring amino acid residues and that tolerate modifications at either their C- or N-terminus without losing their biological activity. Polypeptides that are cyclic, stapled, contain non-natural amino acid residues, or additional modifications cannot be recombinantly produced as fusion polypeptides. However, such polypeptides may be the desired choice for therapeutic applications because they are frequently superior to ‘normal’ linear peptides in terms of protease stability, activity and specificity. But these fusions miss a targeted delivery.
One approach to improve PK/stability and biophysical behavior of therapeutic polypeptides, which can also be applied to those that are cyclic, stapled, or contain non-natural structures, is the chemical or enzymatic conjugation to polymers, for example by PEGylation or HESylation. However, such modifications frequently lead to significant reduction of the biological activity of the polypeptide and can under certain circumstances be the reason for safety or toxicity problems. Also these modifications miss the targeting entity.
A major disadvantage of most existing chemical coupling technologies for stabilization or PK modulation of therapeutic polypeptides is their complexity. Beside the chemical coupling step the methods result in many cases in a mixture of polypeptide derivatives that are connected to the PK-modulating entity with uncertain stoichiometries and/or at undefined positions. Additionally currently used polypeptide modification-technologies often result in strongly reduced or even complete loss of biological activity of the therapeutic polypeptide. In addition, it is difficult to predict pharmacological properties and/or possible degradation routes of the chemical conjugates.
Metz, S., et al. (Proc. Natl. Acad. Sci. USA 108 (2011) 8194-8424) report bispecific digoxigenin-binding antibodies for targeted payload delivery. PK modulation of haptenylated peptides via non-covalent antibody complexation is reported by Hoffmann, E., et al. (J. Contr. Rel. 171 (2013) 48-56). In WO 2012/093068 a pharmaceutical composition of a complex of an anti-dig antibody and digoxigenin that is conjugated to a peptide is reported. Comparison of recombinant immunotoxins against ley antigen expressing tumor cells: influence of affinity, size, and stability is reported by Bera et al. (Bioconjug. Chem. 9 (1998) 736-743). Lee H Pal et al. report anti-tumor activities of immunotoxins made of monoclonal antibody B3 and various forms of Pseudomonas exotoxin (Proc. Natl. Acad. Sci. USA 88 (1991) 3358-3362).
U.S. Pat. No. 5,804,371 reports hapten-labeled peptides and their use in an immunological method of detection. A digoxigenin-labeled peptide (Bradykinin) and its application to chemiluminoenzyme immunoassay of Bradykinin in inflamed tissues are reported by Decarie A., et al. (Peptides 15 (1994) 511-518).
In WO 2004/065569 multi-functional antibodies are reported.
In WO 2014/006124 covalently linked antigen-antibody conjugates are reported.